1. Background of the Invention
Automobile accidents each year result in thousands of fatalities and injuries and cause millions of dollars in property damage. Collisions occur as a result of operator inattentiveness, incompetence, errors in judgement etc. Operator reaction time also plays a part in determining whether a potential collision, once detected, can be avoided. Collisions occur in a number of ways, e.g., rear-end, head-on, broadside, and under a variety of road and terrain conditions, such as two vehicles travelling in opposite directions on parallel paths, two vehicles travelling in the same direction on the same path, around a curve, through a dip or over a crest, at right, oblique or acute angle intersections. Collisions occur on lightly travelled country roads, densely populated highways or city streets, and under all types of weather and lighting conditions, ranging from well lit highways in clear weather to unlit back roads in foul weather.
In order to be effective, an automotive collision avoidance system must operate under all of the foregoing conditions with a high degree of accuracy and reliability. The system must identify and track the location, direction and speed of every other vehicle and be able to signal the operator or the vehicle controls when collision is imminent. The system should also be small and lightweight and should not detract from or interfere with vehicle styling. The system should not issue false alarm signals, even in cluttered environments, should work in the presence of similarly equipped vehicles and should not interfere with the safety or rights of the other motorists, pedestrians or inhabitants of the area in which the vehicle will operate.
2. Prior Art
Automotive traffic control and collision avoidance systems have been proposed. See "Taking the Crush Out of Rush Hour", High Technology Business, March, 1989, pages 26-30; and "Laser Ranging Device Keeps Cars Apart", Winfried Arndt, Photonics Spectra, July 1990, pages 133-134. The proposed systems typically involve radar tracking systems which provide range information by measuring the time delay between transmission of a radio frequency pulse and detection of the pulse reflected from a distant object. Some radar systems are also capable of determining vehicle velocity using the doppler principle. However, radar systems suffer from a lack of good spatial resolution, and require a large antenna to obtain good resolution. For example, at 35 GHz, an antenna size of 1188 millimeters would be required to obtain one degree beam resolution. Using millimeter wave radar at 94 GHz can improve the antenna size, but still requires a 372 millimeter antenna. In either case, the antenna size is inappropriate for automotive implementation without compromising body styling and aerodynamics.
Moreover, while one degree resolution may be adequate for aeronautical applications, such resolution is inadequate for a universally effective and reliable collision avoidance system. Such systems, it will be seen herein, call for a narrow beam resolution of about 1/4 of one degree with a rapid slew rate of over 300,000 times per second over a 60.degree..times.6.degree. field. Such requirements make traditional radar systems impractical for automotive applications.
Laser radar systems are also known, and eliminate the problem of large beam widths by providing a beam having a much shorter wavelength on the order of about 1.0 micrometers. Beam spreads on the order of a few milliradians are possible, but heretofore known laser rangefinder systems employ very high peak power in the transmitted pulses, on the order of 10 megawatts or more. Repetition rates of 1-20 Hz are obtainable with lasers, but such lasers usually must be water cooled to prevent overheating. The power and cooling requirements of these lasers make them impractical for automotive application. In addition, repetition rates on the order of several hundred thousand are necessary under the more stringent collision avoidance applications, which require very high repetition rates, a wide field of view and high spatial resolution. Another problem with some laser rangefinder systems is that the laser beams generally are not eyesafe and may cause eye injury to pedestrains or other motorists.
Aeronautical collision avoidance systems based on beacon tracking are also known. Such systems generally are beacon systems which involve aircraft mounted transmitters and receivers. A transmitter on one aircraft transmits position, direction and velocity information for that aircraft. A nearby aircraft receives the transmitted information and processes the information in conjunction with the corresponding information for the receiving aircraft to determine whether a collision is likely. As will be appreciated, a beacon system requires that both aircraft be equipped with a transmitter, receiver and electronic equipment capable of determining and processing position, direction and velocity information relative to a reference frame common to all aircraft. The accuracy of the system depends upon the accuracy of the information transmitted and processed. Beacon systems are not well suited for automotive applications due to (i) lack of a convenient common reference frame; (ii) expense of equiping all automobiles with the required equipment; (iii) ineffectiveness of the system with respect to automobiles not equipped with the beacon system.
In sum, existing systems suffer from various deficiencies including large size, low scan rate, eye safety, expense, etc.
With regard to motor vehicles, there has also been discussion of vehicle control systems integrated into highways. Such systems typically call for roads provided with electronic guides, superconducting magnets etc. Needless to say, such proposals are extremely expensive from the standpoint of development and implementation, and would only be operative in localities where substantial capital equipment has been integrated into the roadway and automobile.
3. Objects of the Invention
It is therefore an object of the present invention to provide a collision avoidance system.
It is a further object of the invention to provide a collision avoidance system which is compact and readily may be implemented into an automobile.
Another object of the invention is to provide a rangefinder scanner which, among other things, is suitable for use in a collision avoidance system.
Another object of the invention is to provide a collision avoidance system which is capable of distinguishing among and tracking numerous potential collision targets.
Yet another object of the invention is to provide a collision avoidance system which is operable under a wide variety of road and weather conditions.
A still further object of the invention is to provide a collision avoidance system processor which utilizes a single target analysis procedure regardless of the potential collision geometry.
These and other objects and advantages are accomplished in a compact collision avoidance system which may be mounted to an automobile without detracting from or interfering with vehicle styling, and which identifies and tracks potential collision targets electrooptically under a variety of weather and road conditions. While the present invention will be discussed with specific reference to the problem of collision avoidance in automotive applications, it is contemplated that the electro-optical collision avoidance system of the present invention may find application to other fields, albeit with modifications to the operating range, resolution, etc.